Process and apparatus for heating or cooling light solid particles

Abstract

The invention discloses a process and apparatus for the heating or cooling of light solid particles having a low free-fall speed, by means of flowing gas-solid exchangers. The process makes it possible to heat or cool light solid particles dispersed in a gas flow by contacting them with a countercurrent flow of heavy solid particles having a greater final free-fall speed and that are hot or cool in relation to the light particles, thus effecting a heat transfer between the particles.

We claim: 
     
       1. A process for the heat transfer treatment of light solid particles having a low free-fall speed which comprises: (a) dispersing the light particles in a first gas current;   (b) contacting the first gas current, containing the light particles and moving upward along a first baffled path in a reaction zone, with heavy solid particles having a greater free-fall speed and circulating countercurrently in the reaction zone in a loose gravity flow, to effect a first heat transfer between the light particles in the first gas current and the heavy particles;   (c) contacting the heavy particles, having undergone the first heat transfer and circulating countercurrently along a second baffled path in a loose gravity flow, with an upward-moving second gas current, to effect a second heat transfer between the heavy particles and the second gas current;   (d) recycling the heavy particles and   (e) reusing the heavy particles in step (b).   
     
     
       2. A process for the heating of light solid particles which comprises: (a) dispersing the light particles in a first gas current;   (b) contacting the first gas current, containing the light particles and moving upward along a first baffled path in a reaction zone, with hotter heavy solid particles having a greater free-fall speed and circulating countercurrently in the reaction zone in a loose gravity flow, to effect a first heat transfer between the light particles in the first gas current and the heavy particles to produce heated light particles, a heated first gas current and cooled heavy particles;   (c) contacting the cooled heavy particles, circulating countercurrently along a second baffled path in a loose gravity flow with a hotter, upward-moving, second gas current, to effect a second heat transfer between the heavy particles and the second gas current to produce heated heavy particles and a cooled second gas current;   (d) reusing said heated heavy particles in stage (b)   (e) recycling the cooled heavy particles in stage (c); and preferably   (f) reusing the heated first gas current as a part of the second gas current in stage (c).   
     
     
       3. A process for the flash heat treatment or calcining of light solid particles which comprises: (a) dispersing the light particles in a gas current;   (b) contacting the gas current, containing the light particles and moving upward along a first baffled path in a reaction zone, with hotter solid particles having a greater free-fall speed and circulating countercurrently in the reaction zone in a loose gravity flow, to effect a first heat transfer between the light particles in the gas current and the heavy particles to produce heated light particles, a heated gas current and cooled heavy particles;   (c) exposing the heated gas current containing the heated light particles to a flash heat or calcining treatment;   (d) contacting the gas current containing the heat treated light particles and moving upward along a second baffled path with cooled heavy particles, circulating countercurrently in a loose gravity flow, to effect a second heat transfer between the heavy particles and the gas current carrying the treated light particles to produce heated heavy particles, a cooled gas current and cooled light particles;   (e) recycling the cooled heavy particles; in stage (d)   (f) reusing the heated heavy particles in step (b).   
     
     
       4. A process for the flash heat treatment of light solid particles carried out in a single column having at least three heat transfer zones and which comprises: (a) dispersing the light particles in a gas current;   (b) contacting the gas current, containing the light particles and moving upward along a first baffled path in a first heat transfer zone in the lower part of the column, with hotter heavy solid particles having a greater free-fall speed and circulating countercurrently in the column in a loose gravity flow, to effect a first heat transfer between the light particles in the first gas current and the heavy particles to produce heated light particles, a heated first gas current and cooled heavy particles;   (c) exposing the heated gas current containing the heated light particles to a flash heat treatment in an intermediate heat transfer zone;   (d) contacting the heated gas current, containing the heat treated light particles and moving upward along a second baffled path, in a third heat transfer zone in the higher part of the column with cooled heavy particles, circulating countercurrently in a loose gravity flow, to effect a second heat transfer between the heavy particles and the gas current carrying the treated light particles to produce heated heavy particles, a cooled gas current and cooled light particles;   (e) recycling the cooled heavy particles in stage (d)   (f) reusing the heated heavy particles in step (b).   
     
     
       5. Process according to one of claims 1, 2, 3 or 4, wherein the free-fall speed of the heavy particles is between about 10 and 100 times that of the light particles. 
     
     
       6. Process according to one of claims 1, 2, 3 or 4, wherein the heavy particles have a free-fall speed between about 2 and 20 m/s at the ambient temperature and the light particles have a free-fall speed below about 0.2 m/s at the ambient temperature. 
     
     
       7. Process according to one of claims 1, 2, 3 or 4, wherein the heavy particles have a free-fall speed between about 5 and 15 m/s at the ambient temperature. 
     
     
       8. Process according to one of claims 1, 2, 3 or 4, wherein the heavy particles comprise spheres of sand, zircon or vitroceramic having a granulometry between about 1 and 2 mm and a density between about 2.5 and 3.8 g/cm 3 . 
     
     
       9. An apparatus for the heat transfer treatment of light solid particles having a low free-fall speed which comprises: (a) means for dispersing the light particles in a first gas current;   (b) means for contacting the first gas current, containing the light particles and moving upward along a first baffled path in a reaction zone, with heavy solid particles having a greater free-fall speed and circulating countercurrently in the reaction zone in a loose gravity flow, to effect a first heat transfer between the light particles in the first gas current and the heavy particles;   (c) means for contacting the heavy particles, having undergone the first heat transfer and circulating countercurrently along a second baffled path in a loose gravity flow, with an upward-moving second gas current, to effect a second heat transfer between the heavy particles and the second gas current;   (d) means for recycling the heavy particles and   (e) means for reusing the heavy particles in step (b).   
     
     
       10. An apparatus for the heating of light solid particles which comprises: (a) means for dispersing the light particles in a first gas current;   (b) means for contacting the first gas current, containing the light particles and moving upward along a first baffled path in a reaction zone, with hotter heavy solid particles having a greater free-fall speed and circulating countercurrently in the reaction zone in a loose gravity flow, to effect a first heat transfer between the light particles in the first gas current and the heavy particles to produce heated light particles, a heated first gas current and cooled heavy particles;   (c) means for contacting the cooled heavy particles, circulating countercurrently along a second baffled path in a loose gravity flow with a hotter, upward-moving, second gas current, to effect a second heat transfer between the heavy particles and the second gas current to produce heated heavy particles and a cooled second gas current;   (d) means for reusing the heated heavy particles in stage (b)   (e) means for recycling the cooled heavy particles in stage (c); and, preferably,   (f) means for reusing the heated first gas current as a part of the second gas current in stage (c).   
     
     
       11. An apparatus for the flash heat treatment or calcining of light solid particles which comprises: (a) means for dispersing the light particles in a gas current;   (b) means for contacting the gas current, containing the light particles and moving upward along a first baffled path in a reaction zone, with hotter solid particles having a greater free-fall speed and circulating countercurrently in the reaction zone in a loose gravity flow, to effect a first heat transfer between the light particles in the gas current and the heavy particles to produce heated light particles, a heated gas current and cooled heavy particles;   (c) means for exposing the heated gas current containing the heated light particles to a flash heat or calcining treatment;   (d) means for contacting the gas current containing the heat treated light particles and moving upward along a second baffled path with cooled heavy particles, circulating countercurrently in a loose gravity flow, to effect a second heat transfer between the heavy particles and the gas current carrying the treated light particles to produce heated heavy particles, a cooled gas current and cooled light particles;   (e) means for recycling the cooled heavy particles;   (f) means for reusing the heated heavy particles in step (b).   
     
     
       12. An apparatus for the flash heat treatment of light solid particles carried out in a single column having at least three heat transfer zones and which comprises: (a) means for dispersing the light particles in a gas current;   (b) means for contacting the gas current, containing the light particles and moving upward along a first baffled path in a first heat transfer zone in the lower part of the column, with hotter heavy solid particles having a greater free-fall speed and circulating countercurrently in the column in a loose gravity flow, to effect a first heat transfer between the light particles in the gas current and the heavy particles to produce heated light particles, a heated gas current and cooled heavy particles;   (c) means for exposing the heated gas current containing the heated light particles to a flash heat treatment in an intermediate heat transfer zone;   (d) means for contacting the heated gas current, containing the heated light particles and moving upward along a second baffled path, in a third heat transfer zone in the higher part of the column with cooled heavy particles, circulating countercurrently in a loose gravity flow, to effect a second heat transfer between the heavy particles and the gas current carrying the treated light particles to produce heated heavy particles, a cooled gas current and cooled light particles;   (e) means for recycling the cooled heavy particles.   
     
     
       13. Apparatus for the treatment of light solid particles according to one of claims 9, 10, 11, 12, wherein the heat exchanger or heat exchangers comprise a column having packing elements which impose a baffled path on the particles moving through the exchangers. 
     
     
       14. The apparatus according to claim 13 wherein tightness at the dispersion and recycling points for the heavy particles is ensured by fluidized traps and rotary distributors. 
     
     
       15. The apparatus according to claim 13 wherein tightness at the dispersion and recycling points for the light particles is ensured by rotary chambers. 
     
     
       16. The apparatus according to claim 13 wherein the means for recycling the cooled heavy particles is a bucket lift. 
     
     
       17. A process for the cooling of hot light solid particles which comprises: (a) dispersing the light particles in a first gas current;   (b) contacting the first gas current, containing the light particles and moving upward along a first baffled path in a reaction zone, with colder heavy solid particles having a greater free-fall speed and circulating countercurrently in the reaction zone in a loose gravity flow, to effect a first heat transfer between the light particles in the first gas current and the heavy particles to produce cooled light particles, a cooled first gas current, and heated heavy particles;   (c) contacting the heated heavy particles, circulating countercurrently along a second baffled path in a loose gravity flow with a colder, upward-moving, second gas current, to effect a second heat transfer between the heavy particles and the second gas current to produce cooled heavy particles and a heated second gas current;   (d) recycling the cooled heavy particles;   (e) reusing the cooled heavy particles in stage (b); and   (f) reusing a portion of the heated second gas current as a first gas current.   
     
     
       18. An apparatus for the cooling of hot light solid particles which comprises: (a) means for dispersing the light particles in a first gas current;   (b) means for contacting the first gas current, containing the light particles and moving upward along a first baffled path in a reaction zone, with colder heavy solid particles having a greater free-fall speed and circulating countercurrently in the reaction zone in a loose gravity flow, to effect a first heat transfer between the light particles in the first gas current and the heavy particles to produce cooled light particles, a cooled first gas current and heated heavy particles;   (c) means for contacting the heated heavy particles, circulating countercurrently along a second baffled path in a loose gravity flow with a colder, upward-moving, second gas current, to effect a second heat transfer between the heavy particles and the second gas current to produce cooled heavy particles and a heated second gas current;   (d) means for recycling the cooled heavy particles;   (e) means for reusing the cooled heavy particles in stage (b); and   (f) means for reusing a portion of the heated second gas current as a first gas current.